1. Field of the Invention
The present invention is in the field of medical implants having electronic components, such as cardiac pacemakers, defibrillators, cardioverters, neurostimulators, or auditory canal implants. In particular, the present invention relates to the hermetically sealed feedthroughs required in devices of this type for the various electrical connections between internal device electronics and external components. In a special embodiment, the present invention relates to the shielding and/or filtering of electromagnetic interference (EMI) required for such feedthroughs.
Furthermore, the present invention relates to manufacturing method for producing the components according to the present invention.
2. Description of the Related Art
Implantable devices typically comprise a metal housing having a plug connection incorporated therein for receiving external connections, e.g., for electrical stimulation or measuring physiological signals. The hermetic seal of the components situated in the internal area (control electronics, battery) in relation to the environmental conditions, as exist in the inside of the body of the wearer, is of special significance. This places special demands on the feedthroughs of the electrical connections. No corrosion effects may occur here, each individual through contact must be absolutely tight to gas and liquid diffusion.
The prior art is that insulators made of ceramic are used as a carrier in feedthroughs for implants. These are predominantly shaped cylindrically and compressed and sintered as molded parts. As a rule, the electrical through contact is produced via prefinished openings in the ceramic using metallic contact pins (pins). The attachment capability to the implant housing is provided for the ceramic insulator in turn via a metallic flange. Thin, insulation ceramic, and flange are situated in such a way that the pins are enclosed by the ceramic and the ceramic is in turn enclosed by the flange. Such a feedthrough is described, for example, in the documents U.S. Pat. Nos. 5,759,197 and 5,836,992. FIG. 1 shows such a configuration according to the prior art.
Ceramic, flange, and pins are typically soldered hermetically sealed by a brazing process using gold solder. For this purpose, the insulation ceramic must be partially metal-plated beforehand on the soldered surfaces. This coating technology is complex, because individual masks must be used for it. The shape described and the specialization of the individual steps therefore prevent cost-effective manufacturing methods and the use of cost-effective semifinished products for feedthroughs according to the prior art.
Notwithstanding the construction described, alternative approaches are known from the documents U.S. Pat. Nos. 5,620,476 and 5,683,435. Instead of individual feedthroughs having one pin each, narrow ceramics in multilayer construction are used therein. A number of varying electrical feedthrough contacts are applied here as printed conductors to internal layers of the multilayer ceramic. The strip-shaped multilayer ceramic is in turn annularly enclosed by an oval flange, similarly to the contact pin in the conventional construction described, and thus soldered into the housing of the implant as a vertical collective feedthrough. Numerous individual processes and coatings are also required in this technique. In particular, sealing the vertically inserted multilayer ceramic places special demands on the precise fit of the annularly enclosing flange and the peripheral metal plating of the ceramic for the soldering process.
A further problem in feedthroughs for implantable devices is the susceptibility to electrical interference from interference by external electromagnetic fields. Because of the rising amplifier sensitivity on one hand and the increasing external interfering influences on the other hand (radio into the gigahertz range, mobile telephones having strong transmission power operated in the proximity), the demands grow on shielding by EMI filtering. For good filtering, passive or active components must be positioned proximally to the direct inputs and be electrically contacted with the pins and the flange and/or another potential.
The present invention proceeds from the described prior art. It is based on the object of providing an alternative feedthrough, which may be produced cost-effectively and which meets the cited requirements in regard to a hermetically tight incorporation on the implant housing and shielding capabilities. It is based on the further object of providing a manufacturing method for producing a feedthrough according to the present invention. These objects are fulfilled in a feedthrough as claimed herein. Further advantages and special designs of the feedthrough according to the present invention and the manufacturing method are claimed herein.